A recent study uncovered intriguing insights into the impact of oral contraceptives (OCs) and endogenous sex hormones on the brain's fear-processing regions. The findings were published in Frontiers in Endocrinology.
The study was conducted with the participation of healthy adults aged 23-35, focused on individuals who identified as women and fell into different contraceptive use categories. The groups included current OC users, past OC users, women who had never used hormonal contraception, and men. Researchers assessed endogenous sex hormones in saliva and ethinyl estradiol (EE) levels in current OC users. They employed advanced imaging techniques to analyze brain structures associated with fear processing.

When comparing the groups, researchers discovered a sex-related difference: all groups of women had larger gray matter volumes (GMVs) in the dorsal anterior cingulate cortex, a region implicated in fear promotion, compared to men. However, only current OC users exhibited thinner ventromedial prefrontal cortex, a region associated with fear inhibition. Intriguingly, women who had never used hormonal contraceptives had a thicker right anterior insular cortex, regardless of their menstrual cycle phase, compared to past OC users.
While the relationship between endogenous sex hormones and these brain changes remains somewhat unclear, the study revealed that the dosage of EE in current OC users had a significant impact on brain anatomy. Lower doses of EE were associated with smaller cortical GMVs, indicating a potential link between OC dosage and brain structure.
These findings suggest that OC use may influence the structure of brain regions associated with fear and anxiety. Importantly, the effects appear to be reversible, indicating that the anatomical changes related to OC use may not be permanent.
Understanding these effects is critical as they may shed light on structural vulnerabilities linked to anxiety and stress-related disorders. However, the study also points to the need for further research to explore these effects more comprehensively and to uncover any potential long-term consequences of hormonal contraceptive use.
Source:
Brouillard, A., Davignon, L.-M., Turcotte, A.-M., & Marin, M.-F. (2023). Morphologic alterations of the fear circuitry: the role of sex hormones and oral contraceptives. In Frontiers in Endocrinology (Vol. 14). Frontiers Media SA. https://doi.org/10.3389/fendo.2023.1228504